1. Field of the Invention
This invention relates to a rotary drum assembly for forming an agglomerated product from agglomerative materials and more particularly to a rotary drum assembly having a pair of rotating drum members longitudinally aligned with the first drum member having an outlet end portion extending into the inlet portion of the second drum member and pivotally mounted relative thereto for adjusting the slope of the first drum member relative to the second drum member.
2. Description of the Prior Art
In the process of refining coal in the production of coking coal and formcoke, as described in U.S. Pat. Nos. 3,073,351; 3,401,089 and 3,562,783, particulate bituminous coal and finely divided char (the solid carbonaceous residue of coal which has been distilled at a temperature of between 800.degree. and 1400.degree. F) is introduced into a rotary drum. Depending on the type of coal employed in the ratio of coal to char, pitch may also be added as a binder and to increase the strength of the agglomerates formed in the process. The preheated coal and char supply as sensible heat substantially all the heat required to achieve the desired temperature for agglomerating the carbonaceous materials.
The materials are intimately mixed by rotation of the drum. As the constituents are mixed, the coal particles are further heated to such an extent that partial distillation of the coal particles occurs, evolving tar and forming a loosely coherent, plastic sticky mass in the rotary drum. Rotation of the drum breaks up the loosely coherent, plastic mass into relatively fine plastic particles which grow in size as a result of the rolling action of the plastic mass of particulate material in the drum.
During the mixing or ball forming stage the rate of flow of the agglomerative materials through the drum, the rotational speed of the drum and the inclination of the drum relative to the horizontal frame determine the size of the agglomerated product. The agglomerates will continue to grow as determined by these factors until the binder evolved by the coal particles and the pitch binder, if employed, loses its plasticity. Thereafter the agglomerates in the drum rigidify or harden to form uniformly sized particles that are discharged from the outlet portion of the drum. It is of primary importance that the agglomerated product formed be uniformly sized, preferably in the range of between 3/4 to 2 inches. Agglomerates having a size greater than about 2 inches and less than about 3/4 inches are considered unsuitable for use in a conventional blast furnace or other conventional metallurgical processes.
Rotary drums for agglomerating finely divided solid material are disclosed in U.S. Pat. Nos. 2,778,056; 2,695,221 and 1,921,114; British Pat. No. 779,302 and Canadian Pat. No. 627,037 in which a single drum is utilized to perform the steps of mixing, forming and hardening of the agglomerative materials to form the agglomerated product. The agglomerative materials are introduced into the inlet portion of the rotary drum by screw conveyors and an agglomerated product of a preselected size is discharged from the outlet portion of the rotary drum.
The forming stage and the hardening stage in the production of the agglomerated product require varying operating conditions. For example, during the forming stage the rotational speed of the drum should be greater than the rotation speed during the hardening stage in order to control the size of the agglomerated product. Principally, the size of the agglomerated product is controlled by the flow of the agglomerative materials through the rotary drum which, in turn, is controlled by the rate of rotation and the inclination of the drum with respect to the horizontal. Accordingly, the inclination of the drum during the forming stage should be shallower than the slope of the drum during the hardening stage. To provide these varying operating conditions with a single drum arrangement is not possible.
There is need for a rotary drum assembly in the forming of an agglomerated product from agglomerative material in which the rotational speed and angle of inclination of the rotary drum assembly may be adjusted during the agglomeration process.